"It's a family tragedy, so we'll just take it one day at a time," Cubs manager Rick Renteria said after the Cubs' 8-3 loss to the San Francisco Giants on Wednesday.
Castro was scratched from the lineup about two hours before the game. It was the first time he hadn't started a game this season.
"That's life," teammate Anthony Rizzo said. "Anything can happen at any moment. You have to be grateful for a lot of things."
Per league rules, Castro will miss three to seven days. This season, Castro is hitting .284 with 13 home runs and 64 RBIs.